In a wireless communications network, resources such as frequency, time, and antennas can be allocated to transmit a packet. For example, in the downlink of an Orthogonal Frequency Division Multiple Access (OFDMA) based cellular system, the base station can transmit a packet to one or multiple mobile stations using a certain portion of the frequency bandwidth in a particular transmission time interval.
In different OFDMA based communication systems, a portion of the time-frequency resource is sometimes called a resource block (RB) or a virtual resource block (VRB), a resource unit (RU) or a logical resource unit (LRU), or a resource channel (RCH). Further, there are different types of time-frequency resources, such as distributed logical resource unit (distributed LRU) and localized logical resource unit (localized LRU) in IEEE 802.16m systems. Herein, the portion of the time-frequency resource is referred to as a resource unit (RU). Generally, multiple RUs exist in a system. These RUs can be allocated for transmitting data packets. The allocation of these RUs needs to be communicated via signaling messages or control channel messages. For example, in the downlink channel in an OFDM system, in addition to transmitting a data packet, the base station needs to communicate to the intended one or multiple mobile stations the information of the resources allocated to the transmission of the data packet so that the intended one or multiple mobile stations know in which RUs to receive the data packet.
Further, the transmission time can be one or multiple basic time units that may adopt different terms in different standards also, such as subframes or slots. Herein, the time used in a transmission is referred to as a transmission time interval (TTI).